Cellular systems typically employ paging and/or control channels over which a base station may periodically communicate various information to the user equipment (UE) or mobile units, even when the user equipment is in an idle mode (i.e. not currently engaged in a call). For example, a base station may transmit paging indication signals at regular intervals and the user equipment must be configured to receive and analyze these signals in order to receive an incoming call when required.
In order to conserve energy and lengthen battery life, user equipment may be set to enter an idle, or standby, mode when not actively engaged in a call. During standby operation, the user equipment may generally be off, but must partially “wakeup” in time to receive and then analyze paging indication signals. During the wakeup period, various other signals may also be received and analyzed. The analysis may involve, for instance, decoding the paging indication signal from a serving cell and performing measurements on signals transmitted by the serving cell or by neighbor cells, as required, for example, in order for the network to make handoff, or UE to make cell reselection, decisions. The UE will be in deep sleep for the rest of the time.
The power consumption of the user equipment (UE) while in standby mode may be optimized by efficiently monitoring the paging channel. The periodicity and/or duration of wakeup to receive paging information, as well as optimization of power consumption during the wakeup periods, can significantly impact UE performance.
Network configuration, for instance, may impact UE power consumption and performance. Networks may adjust the intervals at which paging signals may be transmitted, which may necessitate a matching adjustment of UE wakeup intervals. This effectively trades off system performance against UE power consumption. In GSM networks for example, paging intervals are measured in terms of MultiFRraMes (MFRM). A MFRM lasts approximately 235 msec. Paging intervals for telephony may typically range between MFRM2 (470 msec) and MFRM9 (2.1 sec). Longer intervals may result in improved UE standby power performance. However the reduced power consumption may result in reduced UE performance (e.g. longer time to identify an incoming call); notably, when paging intervals are missed, as may occur in poor reception conditions or when the network is heavily loaded, further performance degradation, e.g. missed calls, may be experienced. Consequently, in many networks shorter intervals between paging indication signals (thus higher standby power consumption), such as MFRM2/4, and repetitive transmission of paging indication signals have been given preference in an effort to improve system service.